Contactor switch

ABSTRACT

A contactor rated to switch at least 20 amperes in which the movement of a contact arm to engage a moving contact with a fixed contact occurs in two stages, the arm first moving to engage the moving contact with the fixed contact and then pivoting about the fixed contact. The contactor is in two separably connected parts, the first comprising the electromagnet drive system and the second comprising the contact set, main spring, possibly an auxiliary spring, and a microswitch.

D United States Patent 1111 3, 5

[72] Inventor George Eric Minns [56] References Cited 2 A l N :fg England UNITED STATES PATENTS E 1 523 12 1970 2,031,516 2/1936 Tritle 335/192 [45] Patented 971 3,076 073 1/1963 Townsend 335/192 [73] Assignee Dewhurst and Parmer Limited 3,431,522 3/1969 Kryspm 1. 335/194 [32] Priority Jan. 20, 1969 Primary Examiner-Harold Broome [33] Great Britain Attorney-Holcombe, Wetherill & Brisebois [31] 3,230/69 ABSTRACT: A contactor rated to switch at least 20 amperes [54] CONTACTOR SWITCH in which the movement of a contact arm to engage a moving 6 Claims, 3 Drawing Figs. contact with a fixed contact occurs in two stages, the arm first moving to engage the moving contact with the fixed contact (fl H and then pivoting about the fixed Contact. The Contact is in [50] Fie'ld f 335/185 two separably connected parts, the first comprising the elec tromagnet drive system and the second comprising the contact set, main spring, possibly an auxiliary spring, and a microswitch.

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SHEET 3 [1F 3 Hal 4 INVENTOR G- E. M was buil wMv-Mm s ATTORNEYS CONTACTOR SWITCH This invention relates to a contactor.

The invention is particularly applicable to contactors rated to switch currents of the order of 20 a. or more, and particularly direct currents of 50 a. or more.

More particularly the invention relates to a contactor capable of switching electric currents of at least 20 a., said contactor comprising a contact set including at least one fixed contact, a rigid contact arm, and at least one moving contact mounted on said contact am for engaging said fixed contact, a main spring biassing said contact arm mechanically, and an electromagnet which can be energized and deenergized so as to move said moving contact between first and second positions in which it respectively engages with and disengages from said fixed contact.

One problem which arises with such switches is in obtaining sufficient force holding the contacts closed when the coil is energized with the minimum rated operating current, while avoiding contact bounce, which is aggravated by excessive closure force, particularly when the operating current is at its maximum rated value. This problem is particularly troublesome where the contactor is intended for use in an en vironment subject to shocks or vibration, such as an electrically powered vehicle.

Another problem with such switches is that they are quite complex, and difiicult to assemble and adjust.

The invention is characterized in that the movement of said moving contact from said second to said first positions is arranged to comprise first and second parts, said first part comprising displacing said moving contact from said second position into engagement with said fixed contact, and said second part comprising pivoting said contact arm about said moving contact and said fixed contact.

Other features and advantages of the present invention will appear from the following description of embodiments thereof given by way of example, with reference to the accompanying drawings, in which:

' FIG. I is a cross-sectional view of a contactor in accordance with the invention;

FIG. 2 is a plan view of a bank of three of the contactors, two of which have their electromagnet drive systems removed; and

FIG. 3 is a side view of the bank of contactors, with all the drive systems in position.

The contactor shown in the drawings is formed intwo parts. The first part comprises the contact set, which includes an arm carrying the movable contact or contacts, a main spring biassing the contact arm, and a base on which the contact set and main spring are mounted. The second part, comprising the electromagnet drive system is releasably secured to the base. The electromagnet comprises a solenoid having a plunger which is mechanically connected to a member engaging the contact arm, and connecting means are provided for securing the drive system to the base to maintain the contact set and drive system in their operating relation. The two parts can readily be assembled together, and in the preferred em bodiment readily disassembled, giving considerable economies in manufacture and servicing. In fact the two parts can so readily be assembled together that this job can be left to the customer, and the two parts sold separately. It will be appreciated that this itself offers a further economy, since the range of stocks held can be reduced withoutreducing the range of contactors available to a customer. In this connection, stocks need be held only of a single range of drive systems, and of a single range of contact sets, where if complete, assembled contactors were held in stock, a plurality of ranges of contactors with different drive systems for each different contact set would be needed.

The drive system includes a plate to which the other parts of the drive system are secured, and the connecting means comprises a plurality of bolts. A hinge (not shown) can be provided in the connecting means. Preferably the connection between the drive system and the contact set includes an electrically insulating part or parts, and the member in the drive system engaging the contact arm is preferably an electrically insulating foot, so as to isolate the drive system electrically from at least the moving contact of the contact set.

To reduce the risk of contact bounce, the connection between the solenoid and the member engaging the contact arm is resilient.

The contactor includes another important feature which reduces the risk of contact bounce. When the electromagnet is energized in operation, the contact arm, which is rigid, is first displaced against the bias of the main spring until the moving contact engages the normally open fixed contact. The motion of the contact ann then alters, so that in a second displacement, the contact arm pivots about the normally open fixed contact, further compressing the main spring.

In one embodiment, one end of the contact arm engages a pivot point during the first displacement, so that the contact arm pivots in one'sense about the pivot point during the first displacement, before disengaging from the pivot point and pivoting in the opposite sense about the fixed contact during the second displacement.

In another embodiment the contact arm does not pivot substantially during the first displacement,- since the mechanical couple or net couples exerted by the drive system and the main and anyauxiliary springs is or are substantially zero.

Thus, the drive system, the main spring, and any auxiliary spring exert a net couple on the contact arm during the first displacement which is either substantially zero, or which pivots the arm in a sense tending to displace the moving contact towards the normally open fixed contact, and the drive system, the main spring and the fixed contact exert a net couple during the second displacement which is in the sense tending to compress the main spring against the reaction of the fixed contact.

In the speciali case where the contact arm can be considered as thin, and where the forces exerted on the contact arm are generallymutually parallel, the point where the drive system engages the contact arm is disposed between the point where the fixed contact and the main spring engage the arm.

It will be appreciated that the pivoting of the contact arm about the normally open fixed contact is accompanied by a rubbing action between the moving and fixed contacts. This rubbing action assists in keeping the contact surfaces clean.

Turning nowto FIG. 1 of the drawings, the contactor comprises a first part 10 comprising the electromagnet drive system, and a second part 12, including the contact set, and a baseplate. The electromagnet drive system comprises a solenoid 14, an annular yoke member l6 surrounding the solenoid, a plate 8 on which the solenoid l4 and yoke member 16 are mounted, and a plug 20 which also forms part of the yoke, and is mounted on the baseplate 18 to extend into the solenoid along its axis. The armature of the drive system comprises a plunger 22 extending movably along the axis of the solenoid, and the plug 20 and plunger 22 present cooperating surfaces which define an airgap 23 of variable thickness disposed within the solenoid 14. The surface of the plug 20 is recessed, with a generally rectangular profile in section, the surface of the plunger 22 having a complementary projection; this enhances the pull available in the fully open position at the expense of the pull available in the fully closed position. The yoke member 16, plate 18, plug 20, and plunger 22 are all made of low reluctance magnetic material, and to further reduce the reluctance of the magnetic circuit, a collar 24 is mounted as a flange on the yoke member 16, and closely surrounds the plunger 22. A demagnetizing disc 25 is mounted in the recess in the pole piece 22.

The plunger 22 is connected by a rod 26, which extends through the plug 20 and theplate 18, to a foot 28 of insulating material, the rod 26 being a sliding fit in a central recess in the foot 28. The foot 28 has an annular flange 30 at its end nearer the plate 18, and the flange 30 is provided with a raised peripheral lip 32. A resilient diaphragm, covering the flange 30, engages the lip 32 at its outer edge, and the rod 26 is provided with a circumferential abutment 36 which engages the center of the diaphragm 34. The diaphragm 34 provides some resilience in the connection between the plunger 26 and the foot 28. A weak compression spring 38 engages between the plug 20 and the abutment 36, to prevent play in the drive system causing rattling when the contactor is subject to vibra tion.

A microswitch 40 is also mounted on the plate 18, and has an operating button 42 projecting through a slot 43 in the plate 18; the button 42 is connected to the foot 28 by a lever 44 pivoted between the button 42 and the foot 28 on the plate 18 at 46. The microswitch can be used to control auxiliary circuits for the contactor, for instance to indicate that the plunger 22 has been displaced by energization. of the solenoid 14.

The part 12 comprises a baseplate 48 on which the contact set is mounted. The plate 18 is secured relative to the baseplate 48 by four pillars, or spacers, such as 50 and 52, through which extend bolts, such as 54 and 56, in screwthreaded engagement with the baseplate 48. The parts and 12 can readily be separated by undoing the bolts, such as 54 and 56. In this connection, it will be noted that the engagement of the foot 28 with the part 12 is a simple abutment. In some circumstances it might be desirable to include a hinge in the connection between the plates 18 and 48, so that the drive system and contact set could be separated by pivoting the drive system about the hinge. In either case the connection between the plates 18 and 48 is designed to be readily assembled, so that this job can be performed by the customer.

The part 12 comprises a pair of bars 58 and 60 which are connected to respective terminals 62 and 64, and form fixed electrical contacts. The contacts 58 and 60 present opposed contact surfaces between which are disposed moving contacts 66 and 68 of the contact set, the contacts 58 and 60 extending parallel to the plate 12, and the moving contacts being arranged for movement transverse to the plate 12.

The moving contacts 66 and 68 are formed by projections on one end of a contact arm 70, and the contacts 66 and 68 present part-cylindrical curved surfaces for engaging the contacts 58 and 60.

The main spring of the contactor comprises a coil compression spring 72 which engages between a point 74 on the contact arm and a plate 76 of insulating material on the baseplate 48. The foot 28 engages the contact arm 70 on the side opposite the spring 72 at a point between the contacts 66 and 68 and the point 74. The spring 72 biases the contact arm 70 so that the contact 68 normally engages the contact 60. The solenoid 14 is wired so that energization of the solenoid with direct current displaces the plunger 22 and hence the foot 28, to open the contacts 60 and 68, and close the normally open contacts 58 and 66.

A bridge piece 78 extends over the end of the contact arm 70 remote from the contacts 66 and 78. The bridge piece 78 is indented to present a projection 80 towards the arm 70. In the rest position of the contactor, with the coil 14 deenergized, the main spring 72 urges the contact 68 against the contact 60, and the other end of they contact arm 70 against the projection 80. At this latter end of the contact arm 70, a flexible connector cable 82 is secured by a bolt 84 and washer 86 in intimate contact with the contact arm 70, the shank of the bolt 84 being in screw-threaded engagement with the arm 70. The shank of the bolt 84 also extends with a certain amount of clearance through an aperture 88 in the bridge piece 78, to locate the end of the contact arm 70 relative to the baseplate 48 for movement perpendicular to the baseplate. The connector 82 comprises a length of cable formed into a closed loop, the cable being secured to a terminal 90 mounted on a flange 92 of the bridge piece 78.

An auxiliary compression spring 88 is positioned between the washer 86 and the plate 76, to bias the end of the contact arm 70 towards engagement with the indentation 80. The auxiliary spring 94 is very much weaker than the main spring 72, and can be omitted, particularly if the spacing between the contacts 68 and 66 and the main spring 72 is increased relative to the spacing between the foot 28 and the contacts 68 and 66.

In operation, the contactor normally assumes the rest position shown in FIG. 1. When current is now supplied to the solenoid 14, the magnetic flux in the airgap between the plunger 22 and the plug 20 depresses the plunger 22, to displace the contact arm 70, so as to open the contacts 60 and 68. In this embodiment of the invention, the arm 70 pivots about the indentation 80, in a clockwise direction, as seen in FIG. 1, so that the contact 66 is displaced towards the contact 58. It will be appreciated that if the foot 28 were closer to the point 74, and particularly if the spring 88 were omitted, this displacement of the contact arm might be a simple translatory movement, instead of a pivoting movement, with the arm disengaging from the indentation as well as from the contact When the contact 66 engages the contact 58, the motion of the contact an'n changes to a pivoting movement in a counterclockwise direction as seen in FIG. 1 about the contact 58, and at this moment, the diaphragm 34 flexes to absorb some inertial forces. As the foot 28 continues to advance, the contact arm 70 continues to pivot about the contact 58, further compressing the main spring 72, and in this embodiment the auxiliary spring 88 also, until the bolt 84 engages the plate 76.

When the foot 28 is advanced as the solenoid 14 is energized, it picks up the lever 44, which pivots in a clockwise direction as seen in FIG. I, to depress the contact 42 of the microswitch 40. It will be appreciated that the position of the microswitch 40 can readily be adjusted in a direction perpendicular to the plate 18, by inserting spacers of different thickness, and also can be adjusted in a direction parallel to the plane 18 towards and away from the pivot 46, so as to adjust the operating point of the microswitch 40 relative to the movement of the foot 28.

When the solenoid is now deenergized, the contact arm 70 will be returned to its rest position by the main spring 72, assisted by the auxiliary spring 88, if present.

This contactor is rated to switch a direct current of 200 amps. It will be appreciated that with such a high current, the problems, for instance of bounce and cost, are increased because of the size of the parts of the contactor.

FIGS. 2 and 3 show a bank of three of the contactors of FIG. 1 as used in reversing the current to the field winding of a DC motor. It will be appreciated that the contactors are relatively compact, enabling close positioning of the contactors in such a bank, which facilitates electrical coupling of the contactors.

I claim:

1. A contactor capable of switching electric currents of at least 20 amps, said contactor comprising a contact set including at least one fixed contact (58), a rigid contact arm (70), and at least one moving contact (66) mounted on said con tact arm for engaging said fixed contact, a main spring (72) biassing said contact arm mechanically, a support member (48) on which said contact set and main spring are mounted, an electromagnet (l4) releasably connected to said support member, which electromagnet, when energized and deenergized, moves said moving contact between first and second positions in which it respectively engages with and disengages from said fixed contact, and means (74, 84) guiding the movement of said moving contact (66) from said second to said first position and dividing said movement into a first part in which said moving contact (66) is displaced from said second position into engagement with said fixed contact (58), and a second part in which said contact arm (70) pivots about said moving contact (66) and said fixed contact (58).

2. A contactor according to claim 1 comprising an auxiliary spring wherein said main spring, (72) auxiliary spring, (88) and said electromagnet (14,22) exert on said contact arm (70) during at least said first part of said movement a net mechanical couple which is substantially zero.

3. A contactor according to claim 1 comprising an auxiliary spring wherein said main spring (72), auxiliary spring (88), and said electromagnet (14, 22) exert on said contact arm (70) during at least said first part of said movement a net mechanical couple which tends to rotate the contact arm (70) in a sense tending to move said moving contact (66) from said second position towards said first position.

6. A contactor according to claim 5 wherein said contact arm is electrically conductive and is electrically connected to said moving contact (66), and said member (28) is of electrically insulating material. 

1. A contactor capable of switching electric currents of at least 20 amps, said contactor comprising a contact set including at least one fixed contact (58), a rigid contact arm (70), and at least one moving contact (66) mounted on said contact arm for engaging said fixed contact, a main spring (72) biassing said contact arm mechanically, a support member (48) on which said contact set and main spring are mounted, an electromagnet (14) releasably connected to said support member, which electromagnet, when energized and deenergized, moves said moving contact between first and second positions in which it respectively engages with and disengages from said fixed contact, and means (74, 84) guiding the movement of said moving contact (66) from said second to said first position and dividing said movement into a first part in which said moving contact (66) is displaced from said second position into engagement with said fixed contact (58), and a second part in which said contact arm (70) pivots about said moving contact (66) and said fixed contact (58).
 2. A contactor according to claim 1 comprising an auxiliary spring wherein said main spring, (72) auxiliary spring, (88) and said electromagnet (14,22) exert on said contact arm (70) during at least said first part of said movement a net mechanical couple which is substantially zero.
 3. A contactor according to claim 1 comprising an auxiliary spring wherein said main spring (72), auxiliary spring (88), and said electromagnet (14, 22) exert on said contact arm (70) during at least said first part of said movement a net mechanical couple which tends to rotate the contact arm (70) in a sense tending to move said moving contact (66) from said second position towards said first position.
 4. A contactor according to claim 1 wherein said electromagnet comprises a solenoid (14) having a plunger (22) which is releasably connected to said contact arm (70).
 5. A contactor according to claim 5 wherein said plunger (22) is connected to a member (28) which abuts said contact arm (70).
 6. A contactor according to claim 5 wherein said contact arm is electrically conductive and is electrically connected to said moving contact (66), and said member (28) is of electrically insulating material. 